Fiber Optic Network Design Issue

Unanswered Question
Jan 24th, 2009

I am going to design a network of a newly established University and the following is my requirements and present scenario. In this regard I need your help and I hope your input will help me to design a better network. I want solution completely on cisco. We want to establish connectivity of all the blocks via fiber optics cable (Ring topology) as shown in the figure.

The detail is given in the attachment.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Tom Randstrom Sat, 01/24/2009 - 18:35


From an infrastructure standpoint, I would recommend you read two recent articles in Lightwave (links provided below). This will provide you some insights in selecting fibers.

I would recommend deploying a cable containing a mix of both laser optimized multimode fiber (OM-3, 50/125 micron) and singlemode (8/125 micron); depending on your available budget. Given your currently known span lengths, the OM3 MMF will enable you to support the 1Gbps links with the ability upgrade to 10Gbps links in the future (up to 300 meters in length). The OM3 MMF may also support operation to 40/100Gbps; yet currently the industry is saying <100 meters, but are pushing the vendors to reach 150 to 250 meters over this cable. This is where the SMF cable provides future proofing for your network.

At this point, you will have to balance whether you have the budget to include some SMF in the cable sheath. It shouldn't cost any more labor to install the cable; just the added cost/foot for the materials.

I will let others decide on the switches you should use.



Laser-optimized MMF for 1/10-GbE campus backbone


Weighing MMF vs. SMF in premises applications


viyuan700 Mon, 01/26/2009 - 10:42

Which switch or router to use depends on how many users you have,what speed they need etc. Info which only you have.

Regarding ring design, Do you have a different physical path between admin block and server room?

First ,if you dont have then it doesnot make much sense to go with ring design as both cable will go through the same path. If something happens to one cable will happen to other (can be some exception).

Second,cards required for ring like RPR/DPT are only avialble for 7600 series roueter and above. So if your design dont need those router then you cannot make ring.

m_aurangzeb Mon, 01/26/2009 - 22:17

Each block will have 50 nodes.

Yes we do have different path from server room to admn block but at this time the fiber cable goes from Server room to video conferencing block and then admn block. In future we will expand our fiber from admin block to other blocks and the path will be formed in such a way that cable will be again terminated to the server room. in such way it will form ring (it will provide redundant link)

i have Cisco 2821 router. cant i do this without having 7600 series router? i am going to buy core switch for server room. If i do this(fiber ring) with the help of switch, please suggest any switch(core) model, less expensive.

viyuan700 Mon, 01/26/2009 - 22:49

I think you can take a switch have some extra fiber ports instead of router which supports RPR/DPT. I think High end router makes sense when you have large area to cover and dont have too many fiber pair to connect.

Since you have in building wiring i hope you must be having some extra pair of fibers, these extra pair you can use to connect Core switch in server room to admin block or videoconfrencing room via two routes. Means Server room to admin block one link directly and other through different route.

viyuan700 Wed, 01/28/2009 - 19:52

If you connect NOC distribution switch to admin access layer switch, then you can use STP or RSTP for faster convergence.

IF your distribution and access layer switch is layer 3 enabled you can use a EIGRP etc.

RPR/DPT gives you 50msec protectionswitching if you dont need that then you can use any of the above method in your design for protection.


This Discussion